The present invention relates to fuel caps for closing filler necks of vehicle fuel tanks, and particularly to locking fuel caps. More particularly, the present invention relates to locking fuel caps that enable fuel vapor to vent from the tank upon movement of a lock to an unlocked position prior to rotation of the fuel cap in a removing direction.
Conventional fuel caps for closing the filler neck of vehicle fuel tanks generally include a pressure-vacuum vent valve located in the cap to control the pressure within the fuel tank. Whenever the pressure within the tank reaches a predetermined superatmospheric level, the pressure valve portion of the pressure-vacuum vent valve automatically opens to prevent excess pressure build-up. Whenever the pressure within the tank drops to a predetermined subatmospheric level, the vacuum valve portion of the pressure-vacuum vent valve opens to equalize the pressure in the tank. The pressure-vacuum vent valve, in a conventional fuel cap, must be adjusted so that the potential for some vapor pressure to remain in the fuel tank exists at all times. Generally, the pressure maintained within the fuel tank is in the range of 1-2 PSI.
The retention of some level of fuel vapor in the tank is desired for several reasons and normally does not create any problems. However, under certain conditions, pressure from fuel vapor can result in fuel and fuel vapors escaping from the filler neck during removal of the fuel cap. A rapid escape, or surge, of the fuel and fuel vapor from the filler neck after the cap removal can result in emission of fuel vapor in the region surrounding the filler neck.
With larger fuel tanks now being utilized in many vehicles, and particularly with the use of newer, more volatile fuels having higher than normal Reid vapor pressure may be generated in these fuel tanks, particularly in warm or hot weather or after the vehicle has been running for awhile. Therefore, it would be advantageous to provide a fuel cap that allows fuel vapor to be vented from the fuel tank some time during the cap removal operation, but before the cap is actually removed from the filler neck.
Threaded caps that engage threads in the filler neck of vehicles are now widely used because of their ease of installation and removal and because of the excellent sealing characteristics. Most conventional threaded fuel caps include a primary seal that is adapted to engage a sealing lip on the filler neck when the cap is rotated fully in the cap-installing direction. Because unseating of the primary seal can result in a surge of fuel and fuel vapor from the filler neck in warm or hot weather, or after the vehicle has been running for awhile, it would be advantageous to provide a fuel cap that enables fuel vapor to be vented from the tank in a controlled manner before the seal between the primary seal and the filler neck is broken.
Locking gas caps are, of course, very old in the art. Current conventional locking gas caps typically include a threaded closure member and an outer shell with key-lock means for selectively providing a driving connection between the outer shell and the closure member. In such devices, until the key is actuated, the outer shell will simply rotate on the closure member and not disengage the closure member from the filler neck.
Conventional locking fuel caps also incorporate a torque-override feature. See, for example, U.S. Pat. No. 4,342,208 to Evans. The torque-override feature prevents the closure member of the cap from being twisted too tightly on the filler neck, thereby damaging the threads or the gasket which provides a seal between the filler neck and the closure member. The torque-override feature also prevents installing the cap so tightly as to make it difficult to remove from the filler neck.
In conventional locking fuel caps, the key/lock combination controls the driving connection between the outer shell and the closure member, but has no effect on the venting capabilities of the fuel cap. If the fuel cap is to be vented, it must be vented by other means such as breaking the primary seal by partially removing the closure member from the filler neck. A locking fuel cap that enables fuel vapor to be vented from the tank in a controlled manner by merely rotating a key to an unlocked position without breaking the primary seal would provide a substantial improvement over conventional locking gas caps.
According to the present invention, a lockable fuel cap comprises closure means for rotatably engaging the filler neck and shell means for providing a hand grip for rotating the fuel cap relative to the filler neck between a removed position and an installed position. Lock means is coupled to the shell means for selectively locking and unlocking the fuel cap and is movable between a locked position and an unlocked position. The lockable fuel cap also includes vent means for equalizing fuel vapor pressure between the filler neck and the atmosphere through the closure means and means for actuating the vent means in response to movement of the lock means from the locked position to the unlocked position.
In preferred embodiments, the lock means includes a lock cylinder housing for connecting a conventional lock cylinder to the shell means. A plunger and a removal hub cooperate with the lock means to provide a driving connection between the shell means and the closure means for removing the fuel cap. The plunger is coupled to the lock cylinder housing for axial movement relative thereto. The plunger is configured to include drive means for engaging the removal hub which is rotationally locked to the closure means. Rotation of a key turns the lock cylinder to an unlocked position, causing throw members on the lock cylinder to engage ramp surfaces formed on the plunger to drive the plunger into engagement with the removal hub. At the same time, fingers formed on the plunger disengage from the lock cylinder housing and position themselves to maintain the plunger in engagement with the removal hub, even if the key is moved to the locked position. Thus, when the key is turned to the unlocked position, a driving connection is established between the shell means and the closure means which is maintained when the key is returned to the locked position.
A torque-override mechanism is illustratively included in the lockable fuel cap and includes a race and a drive hub. The drive hub is rotationally locked to the shell means and includes a plurality of drive members. Each drive member has a pawl tooth positioned to engage a radially-inwardly projecting lug formed on the race. The pawl teeth are configured with drive faces to engage the radially-inwardly facing lugs during movement of the fuel cap in the cap-installing direction. The pawl teeth further include ramped surfaces which cooperate with flexible arms of the drive members to ratchet past the radially-inwardly facing lugs when the fuel cap is moved in the cap-removing direction. Thus, the drive hub and race cooperate to provide a driving connection between the shell means and the closure only when the cap is moved in the cap-installing direction.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.